Outline

Objective

To report two cases of pilocytic astrocytoma in young adults which transformed over years into Grade IV tumors.

Methods

Review of case records.

Results

A 14-year-old girl with Neurofibromatosis Type I had a biopsy of a pons tumor which was considered inoperable. The initial histology showed a pilocytic astrocytoma. No specific therapy was initiated. The clinical course and MRI controls every 6 months were stable for almost 5 years. In 2004 suddenly new brain stem symptoms presented and MRI showed considerable tumor progression. Two days before scheduled elective surgery for tumor reduction an acute tumor bleeding occurred and emergency subtotal resection was done in a comatose patient. Histology showed anaplastic astrocytoma Grade III. The patient deceased of a second tumor bleeding. Histology of the autopsy material was classified as Grade IV tumor. The second patient without neurofibromatosis underwent in 1988 resection of a right temporal pilocytic astrocytoma at age 8 followed by radiation therapy. A local recurrence was operated upon in 2001 at age 21 and showed now a pilocytic astrocytoma with parts of focal sarcomatous transformation grade III. In 2003 a right frontal meningeoma grade II was removed. In 2004 a second right temporal recurrence needed surgery, however this time a gliosarcoma Grade IV was diagnosed. The patient is currently treated with repeated courses of temozolamide. He recently presented as well with haemorrhage from recurrent tumor, but recovered well from evacuation of the haematoma and tumour resection.

Conclusions

Malignant transformation of Grade I pilocytic brain tumors is generally of extremely rare occurrence. However, one long-time follow-up study reported transformation into grade III in as many as 3 of 36 patients with posterior fossa tumors. The missing NF I gene in neurofibromatosis can not be firmly linked to malignant transformation. Interestingly, it could be shown that sporadic pilocytic astrocytomas even overexpress the NF1 gene. The first case illustrates that resection of pilocytic astrocytomas also in NF1 patients should always be attempted if the expected operative morbidity is within acceptable limits Most of all reported cases with malignant transformation had received initial radiation therapy like our second case, where radiation probably caused growth of a meningeoma grade II as well. The case illustrates why radiation of residual pilocytic astrocytoma after surgery is currently not recommended anymore.